focus

Pronunciation

• IPA: /ˈfəʊ̯.kəs/ (UK); /ˈfoʊ̯.kəs/ (US)^[1]

Etymology

It is borrowed from New Latin focus (“central point”),^[2][3] from Latin focus (“hearth, fireplace”),^{[4][2][5][3][6]} which is of unknown origin.^[5]

Earliest recorded meaning

A point at which rays meet (1644, of sound waves in Barnhart).^[2][3][5]

Semantic evolution

In post-classical Latin focus was used for the fire itself.^[5] Kepler used it in 1604 for a point of convergence in mathematics, probably by analogy with the burning point of a lens, where the heat rays meet.^[5][2] Hobbes introduced it into English in the 1650s,^[5] and in geometry it names a point that defines a curve such as an ellipse (1656).^[7] The figurative sense of a centre of activity or interest is first recorded in 1796.^[2][5] The verb (1775) first meant to bring into focus in optics;^[2][5][7][3] the figurative “to concentrate attention” is from 1807.^[5][7]

Timeline

• 1604 – used by Kepler in its mathematical sense.^[5]
• 1644 – a point where rays meet.^[2][3]
• 1656 – in geometry, a point defining a curve.^[7]
• 1693 – focal.^[2]
• 1775 – verb, to bring into focus.^[7][2][3]
• 1796 – a centre of activity.^[2][5]
• 1807 – verb, figurative, to concentrate.^[7][5]

Modern meaning

Noun

1. A centre of interest, activity or attention.
2. Close or narrow attention; concentration.
3. (physics) A point at which rays of light, heat or sound meet, or from which they appear to spread.
4. The clear and sharp condition of an image, or the adjustment that produces it.
5. (geometry) A fixed point used to define a conic section.
6. The point underground where an earthquake starts.

Verb

1. To concentrate attention or effort.
2. To adjust a lens or the eyes to give a clear image.
3. To cause light or other rays to converge.

Word family

• focuser
• focusable
• autofocus
• overfocus
• prefocus
• defocus
• misfocus

Related words

• focal
• foyer
• fuel
• curfew

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
3. ^ a b c d e f Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
4. ^ The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin
5. ^ a b c d e f g h i j k l Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
6. ^ Random House Webster's Unabridged Dictionary (1999), 2nd ed., New York: Random House
7. ^ a b c d e f Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press